BST capacitors have essentially been developed for radio frequency applications, in particular for mobile telephony. Having a capacitor with an analogically-adjustable capacitance significantly improves the performance, since it enables to adapt the device comprising such a capacitor to the outside environment.
A BST capacitor appears in the form of an integrated circuit (this type of capacitor is also called adjustable integrated capacitor). The capacitance of a BST capacitor is set by the value of a DC bias potential which is applied thereto, generally in a range from a few volts to a few tens of volts, typically between 2 and 20 volts.
The bias voltage of a BST capacitor is generally provided by a dedicated control circuit, performing a high-voltage digital-to-analog conversion, that is, converting a digital configuration word (generally, a byte) into a DC analog voltage to be applied to the capacitor to set its capacitance.
The control or configuration of a BST capacitor now suffers from inaccuracies due, among others, to manufacturing tolerances and temperature-related variations and variations related to the capacitor hysteresis.